[django] Add support for CORS (Cross-Origin Resource Sharing)

Created by: nemesisdesign

We need to make it possible to enable CORS because other applications may need to access some APIs to get data.

We can use this module: django-cors-headers - which is configurable via django settings, we have to make sure we can configure every available setting of this module, possibly using a single ansible variable containing a dictionary.

This feature should be optional and turned off by default now.